RESUMO
Introduction: Whole genome sequencing (WGS) is increasingly used for characterizing foodborne pathogens and it has become a standard typing technique for surveillance and research purposes. WGS data can help assessing microbial risks and defining risk mitigating strategies for foodborne pathogens, including Salmonella enterica. Methods: To test the hypothesis that (combinations of) different genes can predict the probability of infection [P(inf)] given exposure to a certain pathogen strain, we determined P(inf) based on invasion potential of 87 S. enterica strains belonging to 15 serovars isolated from animals, foodstuffs and human patients, in an in vitro gastrointestinal tract (GIT) model system. These genomes were sequenced with WGS and screened for genes potentially involved in virulence. A random forest (RF) model was applied to assess whether P(inf) of a strain could be predicted based on the presence/absence of those genes. Moreover, the association between P(inf) and biofilm formation in different experimental conditions was assessed. Results and Discussion: P(inf) values ranged from 6.7E-05 to 5.2E-01, showing variability both among and within serovars. P(inf) values also varied between isolation sources, but no unambiguous pattern was observed in the tested serovars. Interestingly, serovars causing the highest number of human infections did not show better ability to invade cells in the GIT model system, with strains belonging to other serovars displaying even higher infectivity. The RF model did not identify any virulence factor as significant P(inf) predictors. Significant associations of P(inf) with biofilm formation were found in all the different conditions for a limited number of serovars, indicating that the two phenotypes are governed by different mechanisms and that the ability to form biofilm does not correlate with the ability to invade epithelial cells. Other omics techniques therefore seem more promising as alternatives to identify genes associated with P(inf), and different hypotheses, such as gene expression rather than presence/absence, could be tested to explain phenotypic virulence [P(inf)].
RESUMO
Poor stability of fish hydrolyzed collagen (HC) hampers its applications, especially as food ingredients. The use of liposome as a vesicle can be a potential means to enhance bioactivities and stability of HC. HC from defatted Asian sea bass skin at different levels (0.25%-2%, w/v) were loaded into liposomes prepared from soy phosphatidylcholine (SPC) with various stabilizers (cholesterol (CHO) or glycerol (GLY)). The highest encapsulation efficiency (EE) was found in SPC-CHO-0.5%HC (P < 0.05) (85.42%), while liposome stabilized with GLY had the highest EE (74.54%) for SPC-GLY-0.25%HC (P < 0.05). After lyophilization, SPC-CHO-0.5%HC had higher EE than SPC-GLY-0.25%HC (P < 0.05). Increasing particle size and decreasing negative surface charge were found for both lyophilized samples. Lyophilized SPC-CHO-0.5%HC exhibited higher stability than lyophilized SPC-GLY-0.25%HC during storage at 25 °C for 28 days. Also, higher antioxidant activities in gastrointestinal track model system was found for SPC-CHO-0.5%HC. Thus, SPC-CHO liposome could be used as a promising carrier of HC.